The remaining part of the construction shows that the original wall could reach 8 m in height and was well constructed, an archaeologist said.

Another researcher said the wall’s foundation dated back to the earlier Ly-Tran dynasties from AD 1,000 to 1,400. This shows a continuation of history, culture and construction techniques used to build the citadel through different dynasties from Ly to Le So, he said.

The researchers also found near the site a kiln from the 13th century Tran Dynasty and a large number of broken pottery pieces.

The original royal palaces and most of the structures of the Thang Long Imperial City (former Hanoi) were destroyed in the late 19th century and the ruins are still being excavated today.